Clean up unnecessary (void) casts (microsoft#2280)

Author: AlexGuteniev

stl/inc/functional

@@ -815,7 +815,6 @@ public:
 private:
     _Mybase* _Copy(void* _Where) const override {
         if constexpr (_Is_large<_Func_impl_no_alloc>) {
-            (void) _Where; // TRANSITION, DevCom-1004719
             return _Global_new<_Func_impl_no_alloc>(_Callee);
         } else {
             return ::new (_Where) _Func_impl_no_alloc(_Callee);
@@ -824,7 +823,6 @@ private:
 
     _Mybase* _Move(void* _Where) noexcept override {
         if constexpr (_Is_large<_Func_impl_no_alloc>) {
-            (void) _Where; // TRANSITION, DevCom-1004719
             return nullptr;
         } else {
             return ::new (_Where) _Func_impl_no_alloc(_STD move(_Callee));

stl/inc/variant

@@ -754,7 +754,6 @@ struct _Variant_construct_visitor { // visitor that constructs the same alternat
         disjunction_v<bool_constant<_Idx == variant_npos>, is_nothrow_constructible<remove_reference_t<_Ty>, _Ty>>) {
         // initialize _Idx-th item in _Self from _Source
         _STL_INTERNAL_CHECK(_Self.valueless_by_exception());
-        (void) _Source; // TRANSITION, DevCom-1004719
         if constexpr (_Idx != variant_npos) {
             _Construct_in_place(_Self._Storage(), integral_constant<size_t, _Idx>{}, static_cast<_Ty&&>(_Source._Val));
             _Self._Set_index(_Idx);
@@ -777,7 +776,6 @@ struct _Variant_assign_visitor { // visitor that implements assignment for varia
                 is_nothrow_constructible<_Remove_cvref_t<_Ty>, _Ty>>>) {
         // assign the _Idx-th alternative of _Self from _Source
         if constexpr (_Idx == variant_npos) { // assign from valueless _Source
-            (void) _Source; // TRANSITION, DevCom-1004719
             _Self._Reset();
         } else {
             if (_Self._Which == _Idx) { // same alternative: assign directly
@@ -1349,7 +1347,6 @@ struct _Variant_relop_visitor2 { // evaluate _Op with the contained value of two
         if constexpr (_Idx != variant_npos) {
             return _Op{}(_Variant_raw_get<_Idx>(_Left), _Right._Val);
         } else { // return whatever _Op returns for equal values
-            (void) _Right; // TRANSITION, DevCom-1004719
             return _Op{}(0, 0);
         }
     }
@@ -1475,7 +1472,6 @@ struct _Variant_dispatcher<index_sequence<_Is...>> {
     template <class _Ret, class _Callable, class... _Types, bool _Any_valueless = ((_Is == 0) || ...)>
     _NODISCARD static constexpr _Ret _Dispatch2(_Callable&& _Obj, _Types&&... _Args) {
         if constexpr (_Any_valueless) {
-            (void) _Obj; // TRANSITION, DevCom-1004719
             ((void) _Args, ...); // TRANSITION, DevCom-1004719
             _Throw_bad_variant_access();
         }

stl/inc/xmemory

@@ -563,7 +563,6 @@ struct _Normal_allocator_traits { // defines traits for allocators
     template <class _Ty, class... _Types>
     static _CONSTEXPR20 void construct(_Alloc& _Al, _Ty* _Ptr, _Types&&... _Args) {
         if constexpr (_Uses_default_construct<_Alloc, _Ty*, _Types...>::value) {
-            (void) _Al; // TRANSITION, DevCom-1004719
 #if _HAS_CXX20
             _STD construct_at(_Ptr, _STD forward<_Types>(_Args)...);
 #else // _HAS_CXX20